Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates generally to catheters having an expandable balloon and to premounted balloon expandable stent balloon catheters generally. More specifically, the present invention is directed to dilatation balloon catheters having a removable protective sheath which may reduce potential trauma caused to the stent and/or the balloon during a crimping process.
2. Description of Related Art
Percutaneous transluminal coronary angioplasty (PTCA) is a procedure which is well established for the treatment of blockages in the coronary arteries. Blockages may occur from cholesterol precipitation on the coronary wall which may be in any stage from initial deposit through aged lesions. Coronary arteries may also become blocked due to formation of thrombus.
The most widely used form of percutaneous coronary angioplasty makes use of a dilatation balloon catheter. In typical PTCA procedures, the cardiovascular system of a patient is accessed with an introducer, usually in the groin area. All other devices including a guiding catheter are percutaneously introduced into the cardiovascular system of a patient through the introducer and advanced through a vessel until the distal end thereof is at a desired location in the vasculature. A guide wire and a dilatation catheter having a balloon on the distal end thereof are introduced through the guiding catheter with the guide wire sliding through the dilatation catheter. The guide wire is first advanced out of the guiding catheter into the patient""s coronary vasculature and the dilatation catheter is advanced over the previously advanced guide wire until the dilatation balloon is properly positioned across the lesion. Once in position across the lesion, the flexible, expandable, preformed balloon is inflated to a predetermined size with a fluid at relatively high pressures, such as greater than about four atmospheres, to radially compress the atherosclerotic plaque of the lesion against the inside of the artery wall and thereby dilate the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation catheter may be withdrawn from the patients vasculature and blood flow resumed through the dilated artery.
In angioplasty procedures of the kind described above, there may be restenosis of the artery, which either necessitates another angioplasty procedure, a surgical by-pass operation, or some method of repairing or strengthening the area. To reduce restenosis and strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency, called a stent, inside the artery at the lesion. In general, stents are prosthetic devices which can be positioned within a body cavity, for example, a blood vessel of the body of a living human or in some other difficulty accessible place. A stent generally has a diameter which may be increased or decreased. Stents are particularly useful for permanently widening a vessel which is in a narrowed state, or for internally supporting a vessel damaged by an aneurysm.
Such stents are typically introduced into the body cavity by use of a catheter. The catheter is usually of the balloon catheter type in which the balloon is utilized to expand the stent, which is positioned over the balloon, to place it in a selected location in the body cavity. The stent is expanded to a larger diameter for placement in the vasculature, often by the balloon portion of the catheter. Stents delivered to a restricted coronary artery, expanded to a larger diameter by a balloon catheter, and left in place in the artery at the site of a dilated lesion are shown in U.S. Pat. No. 4,740,207 to Kreamer and U.S. Pat. No. 5,007,926 to Derbyshire.
In advancing an inflation expandable balloon through a body vessel to the deployment site, the stent must be able to securely maintain its axial position on the delivery catheter, without trans-locating proximally or distally, and especially without becoming separated from the catheter. Stents that are not properly secured or retained to the catheter may slip and either be lost or be deployed in the wrong location or partially deployed. In securing a stent to a catheter, however, the stent must be crimped in such a way as to minimize or prevent altogether distortion of the stent and to thereby prevent abrasion and/or reduce trauma of the vessel walls.
In the past, crimping and balloon reduction has been done by hand often resulting in the application of undesired uneven forces to the stent. Such a stent must either be discarded or re-crimped. Stents which have been crimped multiple times can suffer from fatigue and may be scored or otherwise marked which can cause thrombosis. A poorly crimped stent can also damage the underlying balloon.
Recently, stent crimping devices have been disclosed in U.S. Pat. No. 5,546,646 to Williams et al, U.S. Pat. No. 5,183,085 to Timmermans et al., U.S. Pat. No. 5,626,604 to Cottone, Jr., U.S. Pat. No. 5,725,519, to Penner et al., U.S. Pat. No. 5,810,873 to Morales, WO 97/20593, WO 98/19633 and copending U.S. application Ser. No. 09/404,986, filed Sep. 22, 1999 to Klisch et al, the entire contents of each reference being respectively incorporated herein by reference.
One important characteristic of a dilatation balloon catheter as well as a stent delivery catheter is its xe2x80x9cprofilexe2x80x9d, which is determined by the outer diameter (O.D.) of the distal end portion of the balloon and stent when deflated. The outer diameter affects the ease and ability of the dilatation catheter to pass through a guide catheter, through the coronary arteries, and across a lesion. Considerable effort has been made in developing low profile dilatation balloon catheters. U.S. Pat. No. 5,342,307, incorporated herein by reference, discloses a balloon protector sleeve used with a ti-fold dilatation balloon catheter for angioplasty. Because reduction of profile is of significance balloon reduction often includes the use of a first profile reducing xe2x80x9cbi-tubexe2x80x9d as well as one or more smaller balloon protectors. Typically the bi-tube is placed about the balloon after the balloon is folded and wrapped. The bi-tube is typically removed and replaced with one or more balloon protectors suitable for retaining the balloon in the reduced configuration for shipment or storage. Such use of bi-tubes and balloon protectors are also used in prior stent crimping processes as will be described in greater detail below.
Minimization of xe2x80x9cprofilexe2x80x9d is of importance in balloon catheters and stent delivery systems. In addition to securing the stent onto the balloon catheter, the crimping process may also provide the catheter with a reduced profile configuration. Accordingly, the balloon protector of the present invention is particularly directed for use with balloon catheters and stent delivery systems wherein the protector provides the balloon and stent with protection during the crimping process, thereby allowing the stent to be safely secured to the balloon in a reduced profile state.
All U.S. patents, applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
This invention is directed to a crimpable sheath or protector which may be placed onto the balloon carrying portion of a catheter or stent delivery system prior to reduction of the balloon and/or crimping of a stent onto the balloon. The invention eliminates direct contact between the crimping apparatus and the stent and/or balloon. The larger size and potential surface area of the protector allows for minimization of loading forces and allows the catheter to achieve an optimum profile while minimizing trauma to the underlying balloon and/or stent.
In at least one embodiment of the invention, the inventive balloon protector may be characterized as a polymer sleeve or tube which includes at least one fiber or stripe of relatively rigid material embedded into the polymer material. The fiber or fibers may be configured and oriented in any manner. For example: the fiber(s) may be longitudinally, radially, and/or helically, oriented relative to the longitudinal axis of the protector. The fibers may also be braided together to form a net like configuration. The fiber may be uniformly dispersed throughout the protector body or may be configured with a variety of uniform or non-uniform patterns of dispersion as may be desired.
In at least one embodiment of the invention, the protector is employed with a catheter having an expandable distal portion constructed and arranged for expanding the outer diameter of the catheter from a contracted state to an expanded state. The distal portion of the catheter comprises a balloon which is folded or otherwise collapsed, and is expandable to an expanded condition. The balloon protector may comprise a removable sleeve.
In at least one embodiment of the invention, the sleeve is constructed from at least two materials, wherein the second material is characterized as one or more strands of a rigid material or braids of relatively hard material suspended within or by the first material.
A description of the manufacture of a type of dual material sleeve may be found in U.S. patent application Ser. No. 09/668,496, filed Sep. 22, 2000, to Yang as well as in the related U.S. patent application Ser. No. 09/716,757, filed Nov. 20, 2000, the entire contents of both references being incorporated herein by reference.
The inside diameter of the protector is sized to allow for minimal loading force thereby allowing for ready insertion of the distal end of the balloon catheter into the protector. Because the protector is suitable for use with virtually any size of balloon catheter the inner diameter may range from 0.5 mm to over 10.00 mm if desired. However, typically the protector will have an inner diameter of 0.75 mm to about 5.0 mm.
In use the protector sleeve is positioned around the balloon, and optionally over a stent, prior to reduction of the balloon or crimping of the stent onto the balloon surface. Alternatively, the stent may also be loaded onto a reduced balloon after the protector has been placed thereon. The combined balloon/protector apparatus may then be inserted into a stent crimping apparatus such as those described in the references cited above. Other crimping devices which may be used include but are not limited to the TOMINATOR(trademark) crimping device available from Machine Solutions of Flagstaff, Ariz.
The protector prevents direct contact between the crimping apparatus and the balloon as well as the stent. By preventing direct contact between the crimper and stent, the protector of the present invention allows stents having relatively fragile stent coatings, such as are known to be used in drug delivery applications to be crimped onto a balloon without causing damage to the stent or the relatively delicate coatings. Some examples of stents have drug delivery coatings are described in U.S. Pat. No. 5,972,027 and copending U.S. application Ser. No. 09/420,094, filed Oct. 18, 1999 to Johnson, the entire contents of both of which being incorporated herein by reference.
After reduction or crimping of the catheter and protector, the protector provides a compressive force to retain the balloon in a reduced configuration. The protective sleeve is removed from the catheter prior to use of the catheter.
The present invention also provides for an improved process for applying a balloon protector by providing a crimpable balloon protector which does not require the use of a bi-tube for initial balloon preparation. As may be known, the application of many prior balloon protectors require several steps. For example, applying a prior balloon protector may require the following steps: Loading the bi-tube onto the shaft the of a balloon catheter, then folding the balloon into a desired configuration followed by wrapping the folded balloon. The bi-tube is then slid over the wrapped balloon. Next, the balloon and bi-tube are heat set during the curing process of the shaft coating of the catheter. Following the heat set process, the bi-tube is removed from the balloon and a the smaller diameter balloon protector is placed over the balloon in order to improve profile and to protect the balloon during shipment and storage.
By providing a crimpable balloon protector as described herein, the present invention eliminates the need for a bi-tube and thus the process steps associated with the bi-tube.
In at least one embodiment of the invention the, the invention provides for an improved method for applying the present balloon protector to a balloon. At least one embodiment of the inventive method includes applying the present balloon protector to a formed balloon. The combined balloon and protector is then crimped. The crimping action reduced the profile of the balloon and simultaneously wraps the balloon. The combination balloon and protector is now in condition for shipment and/or storage. The protector remains on the balloon until the balloon is ready for use.
Similar to the process for applying a prior type of balloon protector, prior systems of crimping a stent onto a balloon and applying a stent protector often require numerous steps. For example, a application of a stent protector may require the following steps: folding the balloon, wrapping the balloon, sliding the bi-tube over the balloon, heat setting the balloon, loading the stent onto the balloon, crimping the stent, and finally loading a stent protector over the stent. By providing a crimpable stent protector, the present invention provides a stent protector which may be placed over the stent prior to crimping. As a result, the stent is protected during the crimping process as the blades of the crimper are not able to directly.
In at least one embodiment of the invention a first crimpable balloon protector may be applied to a balloon as described above. After crimping the balloon and protector, the balloon protector is removed from the balloon and a stent is loaded onto the balloon. A a crimpable stent protector may then be placed over the stent. The entire apparatus is then crimped. The crimpable stent protector is removed prior to use of the stent delivery catheter.
In at least one embodiment of the invention the protective sleeve may have one or more slits along its length such as are described in U.S. Pat. No. 6,152,944.
In at least one embodiment of the invention the protective sleeve may include one or more longitudinally oriented indentations or grooves. These indentations may be characterized as scoring on the inside, outside or both surfaces of the protector. The presence of scoring provides additional flexibility to the protector and allows the protector to be reduced in diameter, such as is caused by the crimping process, without distorting the general shape of the protector. The indentations may extend across the entire length of the protector and may have a variety of shapes and configurations.